Bayonet-style circuit breakers or fuses serve to protect an electrical system such as a transformer from overload (or transformer failure) resulting in a short circuit. With these devices, a fuse is inserted into a tubular fuse housing mounted in a tank and having a pair of contacts in its lower end. A typical fuse housing device is disclosed in U.S. Pat. No. 5,204,654, entitled "Fuse Housing Having Fluid Sealing Assembly," and is hereby incorporated herein by reference in its entirety.
Bayonet-style fuses are designed to operate under oil and be easily replaceable after operation. They are installed by attaching it to one end of a fuse holder which is then pushed through the opening in the transformer tank wall and into the tubular fuse housing until the fuse is submerged in oil between the two contacts. The opposite (or upper) end of the fuse holder seals the top opening in the fuse housing. After the fuse has operated, the fuse and holder are withdrawn from the housing and a new fuse is attached to the holder and inserted.
While the foregoing design allows quick removal of the fuse, it requires the air-oil interface to be well below the tank wall opening to prevent oil from draining through the tank wall opening in the fuse housing as the fuse and fuse holder are withdrawn. Even with the air-oil interface below the tank wall opening, certain factors like heat and pad-tilt can cause the oil level to rise to a point above the opening in the tank wall. For example, on larger pad-mounted transformers, temperature induced oil height variations cause the oil level to fluctuate between approximately -2.5 inches and +3.25 inches on a 72 inch high tank. In addition, a pad-tilt angle of 2 or 3 degrees can shift the oil height an additional 1 inch on a 40 inch deep (front to back) tank.
When the fuse is removed, oil often escapes from the fuse housing opening causing contamination of the transformer oil and possible damage to rubber termination systems mounted onto the transformer front plate. This spillage is more likely when the oil height is elevated. It also is common for oil that has escaped to spill onto the floor on which the transformer is mounted. This, especially when unseen or not cleaned properly, results in a hazardous work environment for those who replace the fuses and others who work with or nearby the transformer tanks.
Consequently, devices for capturing the oil that escapes the confines of the transformer tank when the fuse is removed have been designed and implemented to alleviate the problems resulting from dripping oil. Such devices, called drip guards or drip trays, usually are mounted to the upper end of the fuse holder just outside the wall of the transformer to prevent dripping of oil or other insulating fluids onto molded rubber terminators, cables and arresters during removal of the bayonet-style fuses. The trays protect rubber products that may not be chemically compatible with the dielectric fluid.
One such drip tray is the RTE.RTM. Bay-O-Net Fuse Assembly Drip Guard, manufactured by Cooper Power Systems, Inc. of Waukesha, Wis. Another is a drip tray manufactured by Central Moloney, Inc. of Pine Bluff, Ark. A third is an oil drip shield manufactured by Howard Industries, Inc. of Laurel, Mass.
One drawback of these conventional drip trays, however, is that they are cumbersome to operate and mount on a fuse holder, typically requiring two free hands. Another drawback of these conventional drip trays is that they do not have or maintain a firm mount on the fuse holders. It is, therefore, desirable to provide a clamp for drip tray that facilitates mounting of the drip tray on a fuse holder and improves the strength of the mount itself.